A blower has a centrifugal multi-blade fan that has blades around a rotation axis and a casing that houses the centrifugal multi-blade fan. The centrifugal multi-blade fan satisfies a relation of d1/h1≥5, in which d1 is a diameter of a part having the blades, and h1 is a height of the blades in an axial direction of the rotation axis. A part of the casing on one side in an axial direction of the centrifugal multi-blade fan has an air suction port. A part of the casing on the radial outer side of the centrifugal multi-blade fan has an air passage through which air blown from the centrifugal multi-blade fan flows. The casing has an enlargement portion that enlarges the air passage on at least one of the one side and an other side in the axial direction as the casing extends toward the radial outer side.